Complement the u16, u32 and u64 helpers with a u8 variant to ease
accessing byte-sized values.

This helper will be useful for Realtek Digital Home Center platforms,
which store some byte and sub-byte sized values in non-volatile memory.
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200722100705.7772-7-srinivas.kandagatla@linaro.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>